Method for treatment of silicone emulsion waste by chemical addition

ABSTRACT

A method for treating silicone emulsion waste includes the steps of adding base chemical materials to the silicone emulsion waste in an amount effective to cause separating of the silicone emulsion waste. The added chemicals separate the silicone emulsion waste into silicone oil and an emulsion-free water. The components can be separated, with the silicone oil laden liquid being sent to an incinerator and the emulsion-free water being sent to a wastewater treatment plant. The base chemicals can include sodium hydroxide, sodium carbonate, sodium chloride and/or combinations thereof. To enhance separating of the silicone emulsion waste, the silicone emulsion waste can be heated prior to the addition of the chemicals. Also, by recycling the treated water and adding the same to the silicone emulsion waste and base chemicals separation of the silicone emulsion waste can be enhanced.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 09/467,565,filed Dec. 20, 1999, which is hereby incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

The invention relates to a method for the treatment of wastes containingsilicone emulsions for separating silicone oil and water from thewastes. In particular, the invention relates to a method for separatingthe emulsion by the addition of chemicals, such as, but not limited to,sodium hydroxide, sodium carbonate, and sodium chloride, or combinationsof these chemicals, to produce two separate phases containing siliconeoil and water.

FIG. 1 schematically illustrates a prior system for silicone treatment.In FIG. 1, silicone emulsions are produced in a batch method, such as,but not limited to, making a surfactant blend containing different typesand concentrations of emulsifiers and biocides. The surfactant blend ismixed with silicone oil to form a surfactant paste. Next, the surfactantpaste is diluted with water to form emulsion products. A majority of thewaste is generated when mixing vessels and lines are cleaned fortransition to a different silicone emulsion grade product.

A current practice for cleaning the tanks and lines includes washingmixing tanks and lines in cleaning stages. In the first cleaning stage,the tanks are filled to approximately ⅓ of their capacity, and the washwater is recirculated throughout the tanks and lines. This wash water,which contains the majority of the emulsions, is mixed with otherwastes, and can be burned in an incinerator. The cost of running anincinerator, which burns mostly water, is high, and often the wash waterload to the incinerator exceeds its capacity. However, subsequent washescontain very little emulsions, and can be sent directly to a wastewatertreatment plant (WWTP).

Presently, chemicals are available that can be used to break or separateemulsions. The choices of chemicals depend on the specific compositionsof the emulsions containing wastes. There are several commerciallyavailable emulsion separators. In testing, some cationic surfactants,such as Atlas-G265 and G250, manufactured by ICI Surfactants®, failed toadequately separate the emulsion. Likewise, Triton X-50 manufactured byUnion Carbide® and sodium dodecylbenzene sulfonic acid could notadequately separate the silicone emulsions.

Other general types of emulsion separators that were tested for theirability to separate the silicone emulsion include quaternary polyamide,polyamide polymer, aluminum salts, ferric sulfate, polyquaternaryammonium chloride, polyamine, and a sodium aluminate solution whichcontains 20-40% sodium aluminate and 5-10% sodium hydroxide. All ofthese, except sodium aluminate, failed to adequately separate thesilicone emulsion. However, to separate the emulsion, 13% volume basisof sodium aluminate solution must be added. This value may be too highand may result in a costly method.

Therefore, a need exists to develop effective methods for separatingsilicone oil and water from emulsion wastes and to reduce the costassociated with the disposal of such wastes.

SUMMARY OF THE INVENTION

One aspect of the invention provides chemicals, such as sodiumhydroxide, sodium chloride, sodium carbonate and/or a combinationthereof, to separate the emulsions and separate the emulsions intosilicone oil and water. Another aspect of the invention enhancesemulsion separating by heating the emulsion prior to the addition of thechemicals.

Still another aspect of the invention reduces the amount of chemicals toseparate the emulsion by recovering recycled water and including therecovered water in the method, as embodied by the invention.

According to an embodiment, a method for treating silicone emulsionwastes includes the steps of adding base chemical materials to theemulsion waste in an amount effective to cause separating of the waste.The added chemicals separate the emulsion wastes into silicone oil ladenliquid and emulsion-free water. The components can be separated, withthe silicone oil laden liquid being sent to an incinerator and theemulsion-free water being recycled in a waste water treatment plant.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will become apparent fromthe following description of embodiments of the invention, which refersto the accompanying drawings, wherein:

FIG. 1 is a schematic perspective view of a known method for producingsilicone emulsions;

FIG. 2 is a schematic perspective view of a treatment method, asembodied by the invention; and

FIG. 3 is a plot of water recovered percentage of as a function ofpercentage of sodium carbonate added, as embodied by the invention.

DETAILED DESCRIPTION OF THE INVENTION

A silicone emulsion typically comprises a mixture of silicone oil andwater, which can be stabilized by a surfactant blend. The surfactantblend comprises a combination of at least one of nonionic, anionic, andcationic surfactants. Waste from the production of silicone emulsionscan comprise approximately 50% of waste from the method that is sent toan incinerator 30. This stream can be intercepted before mixing andcombined with other materials, so that water can be removed. Thereby,the wastewater load that is sent to the incinerator 30 can be reduced.

FIG. 2 is a schematic perspective view of a treatment method, asembodied by the invention. In FIG. 2, the silicone emulsion waste can beseparated by adding chemicals in an amount that is effective to separatethe silicone emulsion waste. The silicone emulsion waste in reservoir 10can be fed via conduit 12 to mixing tank 14.

Chemical materials for separating the silicone emulsion waste arecontained in a separate tank 16. These chemicals can be pumped from thetank 16 to a mixing tank 14 via a conduit 18. In mixing tank 14, whenseparated, the remaining emulsion or silicone oil 20 will float on topof the emulsion-free water 22, which can be easily separated. Theemulsion-free water 22 can be drained to a water tank 24. The siliconeoil 20 can be transferred to an oil tank 26. The silicone oil 20 can berecycled or incinerated. The emulsion-free water 22 can be recoveredfrom the emulsion by separating, and can be discharged to a wastewatertreatment plant 28.

A series of experiments were performed to determine the appropriatechemicals for separating the silicon emulsions. In the followingdescription, the values are approximate, unless otherwise specified. Theterm “base material” means a basic compound or admixture that has a pHlevel in a range between about 9 to about 14. For example, basematerials such as, but not limited to, 8% NaOH or 8% Na₂CO₃ areeffective base material, as embodied by the invention.

A suitable range of sodium hydroxide mixed with the silicone wasteemulsion in an amount from about 8 to about 12%. Also, a suitable rangeof sodium hydroxide mixed with the silicone waste emulsion is in anamount from about 3 to about 8%. A suitable range of sodium carbonatemixed with the silicone waste emulsion is in an amount from about 3 toabout 10%.

The amount of base materials can be reduced by mixing NaOH and Na₂CO₃with NaCl. For example, but not limited to, a mixture of 6% NaCl with 4%Na₂CO₃ or 0.5% NaOH is effective to reduce the amount of base material,as embodied by the invention. Further, an increase in temperature, forexample, heating the emulsion to 75° C., enhanced emulsion separating.Increasing the temperature further, such as, above 80° C., combined withthe addition of NaCl may also be effective to separate emulsions. Also,use of the water recovered by the treatment can reduce the addition ofchemicals.

In the experiments, several silicon emulsion samples were obtained anddiluted with distilled water, thus simulating dilution that occursduring the washing or cleaning at a silicone manufacturing plant. Thetype of surfactant varied for different emulsion grades. The resultingsilicone emulsion wastes are indicated by Samples 1-8, and containedsilicone oil in a range from about 4.5 to about 10% and with totalsurfactants in a range from about 0.3% to about 1.03%, as listed inTable I.

TABLE I Sample % Si Oil % Total Surfactants 1 4.5 0.59 2 5.6 unknown 36.5 0.76 4 6.5 0.54 5A 6.5 0.67 5B 7.5 0.77 6 9.0 0.30 7 9.0 0.41 8 10.01.03

Advantages of the method, as embodied by the invention, are discussed inthe following examples of the method, as embodied by the invention.

EXAMPLE 1

A 10 milliliter (ml) aliquot was taken from each of the nine samples,which are listed above in Table I. At room temperature (25° C.), sodiumhydroxide (NaOH) in pellet form was mixed into each sample until aseparation in the silicone emulsion waste was visibly detected. Theexperiments were repeated with the 10 ml aliquots preheated to 75° C.before adding the NaOH. The results are listed in Table II. The percentNaOH for separation of the silicone emulsion waste is based on a mass ofNaOH added per mass of the aliquot.

TABLE II Approximate % NaOH Added Sample 25° C. 75° C. 1 10 7 2 10 3 311 4 4 11 3 5A 9 7 5B 11 8 6 12 5 7 10 4 8 N/A 4

The experiment illustrates that NaOH can be used to separate varioussilicone emulsion wastes. It also either that a lower amount of NaOH maybe needed to separate the silicone emulsion waste when the siliconeemulsion waste is provided at a higher temperatures.

EXAMPLE 2

Silicone emulsion waste separating was attempted with sodium carbonate(Na₂CO₃) in this Example because the cost of NaOH is high. A 10 mlaliquot was taken from each sample. At 75° C., Na₂CO₃ (25% solution) wasmixed into each sample until a separation in the silicone emulsion wastewas visibly detected. The percent Na₂CO₃ needed to separate the siliconeemulsion waste can be based on a mass of Na₂CO₃ added per mass of thealiquot.

TABLE III Sample Approximate % Na₂CO₃ Added 1 5.5 2 3.4 3 4.2 4 6.8 5A6.0 6 6.9 7 5.8 8 3.8

The results listed in Table III illustrate that approximately the sameamount of sodium carbonate can separate the silicone emulsion waste in asimilar effectiveness as sodium hydroxide at 75° C.

EXAMPLE 3

A 20 ml sample was taken from Sample 1 and heated to 75° C. PowderNa₂CO₃, which corresponds to 6.7% (mass Na₂CO₃/mass silicone emulsionwaste) was added. The silicone emulsion waste was allowed to separateand the emulsion-free water was drained. The water recovery wascalculated based on the total amount of water in the silicone emulsionwaste. The experiment was repeated with 8.3% and 10% Na₂CO₃ added. Asillustrated in FIG. 3, the water recovery increases as the amount ofadded Na₂CO₃ increases. At 10% Na₂CO₃, approximately 95% water can berecovered.

EXAMPLE 4

A mixture of silicone emulsion wastes was made using equal amounts ofSamples 1, 4, and 6, above. Experiments were conducted with 20 mlaliquots heated to 75° C. In the first experiment, powder Na₂CO₃ wasadded until greater than 90% water recovery was achieved. This valuecorresponded to 8.5% Na₂CO₃. For the second experiment, sodium chloride(NaCl) ions equal to ions from 8.5% Na₂CO₃ were added. The correspondingamount of Na₂CO₃ that is added to achieve at least 90% water recovery is4.7%. Similarly, the experiment was repeated using Na₂CO₃ as a basematerial. When the same amount of salt was added, 0.5% Na₂CO₃ is neededto completely separate the mixture of silicone emulsion wastes. Theseresults can be reproduced using a mixture of silicone emulsion wastesamples 2, 4, 5A, and 8.

These results indicate that Na₂CO₃ or NaOH in the method, as embodied bythe invention, may be reduced by adding NaCl. Cost analysis shows thatsavings can be made by using low salt and low base material amounts.

EXAMPLE 5

A mixture of silicone emulsion wastes was made that comprises of equalparts of Samples 2, 4, and 8, and a half part of Sample 5A. Experimentswere conducted with 20 ml aliquots heated to 75 C. Salt (NaCl) was addedin varying amounts, and the mixture was heated until the siliconeemulsion waste was completely separated.

The results are listed in Table IV illustrate that NaCl can be usedalone to separate the silicone emulsion wastes, however, slightly highertemperatures may need to be reached. Other tests illustrated that saltconcentrations greater than 7% had little if any effect on theseparating temperature.

TABLE IV % NaCl Separate Temperature (E C) 3 93 5 91 6 84 7 81

EXAMPLE 6

Using the same mixture of silicone emulsion wastes in Example 4, 20 mlof silicone emulsion wastes was separated with 1.71 g Na₂CO₃ at 75 C(Experiment A). 10 ml of treated water from Experiment A was added to 20ml of the mixture of silicone emulsion wastes (Experiment B). At 75° C.,the silicone emulsion wastes of Experiment B did not separate, so Na₂CO₃was added. Only 0.48 g of Na₂CO₃ was needed to completely separate thesilicone emulsion waste. Further, 10 ml of treated water from ExperimentB was added to 20 ml of the mixture of silicone emulsion wastes(Experiment C). This addition alone did not separate the siliconeemulsion waste, and Na₂CO₃ was added. 1.79 g of Na₂CO₃ was added toseparate the silicone emulsion waste. The test results indicate thatrecycling the treated water back to the method, as embodied by theinvention, can decrease the chemical materials' requirement. However,the additional chemical materials' requirement surpasses the originalrequirement as water recycling is continued. This result can be possiblydue to surfactant build-up in the water.

While the foregoing description includes many details and specificities,it is to be understood that these have been included for purposes ofexplanation only, and are not to be interpreted as limitations of thepresent invention. Many modifications to the embodiments described abovecan be made without departing from the spirit and scope of theinvention.

1. A system for the treatment of silicone emulsion waste consistingessentially of: a silicone emulsion waste reservoir containingsurfactant stabilized silicone emulsion waste; at least one chemicaltank containing a basic compound or admixture that has a pH of betweenabout 9 and about 14 for separating the silicone emulsion waste; atleast one mixing tank in communication with the silicone emulsion wastereservoir and the at least one chemical tank, wherein the siliconeemulsion waste and the basic compound or admixture are mixed in themixing tank and the surfactant stabilized silicone emulsion waste isseparated into a silicone oil laden liquid and emulsion-free water; awater tank which receives the emulsion-free water from the mixing tank;and an oil tank which receives the silicone oil laden liquid from themixing tank.
 2. The system of claim 1 wherein the basic compound oradmixture comprises sodium hydroxide.
 3. The system of claim 2 whereinthe sodium hydroxide is provided in a concentration of from about 8% toabout 12%.
 4. The system of claim 2 wherein the basic compound oradmixture includes sodium chloride.
 5. The system of claim 1 wherein thebasic compound or admixture comprises sodium carbonate.
 6. The system ofclaim 5 wherein the sodium carbonate is provided in a concentration offrom about 3% to about 10%.
 7. The system of claim 5 wherein the basiccompound or admixture includes sodium chloride.
 8. A system for thetreatment of silicone emulsion waste consisting essentially of: asilicone emulsion waste reservoir containing surfactant stabilizedsilicone emulsion waste; at least on chemical tank containing a basiccompound or admixture that has a pH of between about 9 and about 14 forseparating the silicone emulsion waste; at least one mixing tank incommunication with the silicone emulsion waste reservoir and the atleast one chemical tank, wherein the silicone emulsion waste and thebasic compound or admixture are mixed in the mixing tank and thesurfactant stabilized silicone emulsion waste is separated into asilicone oil laden liquid and emulsion-free water; a water tank whichreceives the emulsion-free water from the mixing tank; an oil tank whichreceives the silicone oil laden liquid from the mixing tank; and anincinerator, in communication with the oil tank, for treatment of thesilicone oil laden liquid.
 9. A system for the treatment of siliconeemulsion waste consisting essentially of: a silicone waste reservoircontaining surfactant stabilized silicone emulsion waste; at least onechemical tank containing a basic compound or admixture that has a pH ofbetween about 9 and about 14 for separating the silicone emulsion waste;at least one mixing tank in communication with the silicone emulsionreservoir and the at least one chemical tank, wherein the siliconeemulsion waste and the basic compound or admixture are mixed in a mixingtank and the surfactant stabilized silicone emulsion waste is separatedinto a silicone oil laden liquid and emulsion-free water; a water tankwhich receives the emulsion-free water from the mixing tank; an oil tankwhich receives the silicone oil laden liquid from the mixing tank; and awastewater treatment plant, in communication with the water tank, fortreatment of the emulsion-free water.